Indicating mechanism



'l Feb. 11, 1 947.

C. M. ANGEL- EVAL INDICATING MECHANISM Filed, March 21, 1945 l l Z7 a@ 25 ,Z7

Zzdf 0215.' y

Ms-Maf gli@ Jsp/llhck aria' Q9. M A? Patented Feb. 11, 1947 INDICATING MECHANISM Charles M. Angel, Huntington, VJ. Va., and Joseph B. Blackburn, Richmond, Va.

Application March 21, 1945 Serial No. 583,990

(Cl. ,E60- 142) 3 Claims.

This invention relates in general to temperature indicating mechanism and has more particular reierence to thermo-responsive electrical switch assemblies which open or close an electrical circuit when the switch assembly is brought to a predetermined temperature.

While the present invention has commercial applicability wherever it is desired to indicate, signal, control, or alter a program upon the attainment of a predetermined temperature at a preselected point, the invention particularly aims to provide means automatically indicating the location of overheated journal boxes or bearings therein in railway cars, locomotives, or similar rolling stock.

Heretofore it has been customary to have an inspector examine the journal boxes of railroad cars, locomotives or other rolling equipment, in various stations, or terminals. Such personal, individual inspection usually fails to locate hot boxes until the overheating has progressed to such a degree that damage is done to the journals or bearings. Such damage can, and in the past has, resulted in wrecks with attendant loss f lift and property.

A principal object of the present invention is the provision of a thermo-responsive electrical switch assembly adapted to be incased in a well inserted into the journal box bearing container, or housing of a railway car, locomotive, or other rolling equipment and placed in an electrical circuit which includes signalling, indicating, or controlling means located within the car or the train of which the car is a part.

An object oi one embodiment of the present invention is the provision of an electrical switch assembly which will interrupt an electrical circuit when said switch is exposed to a predetermined tomperature, thereby turning off a safety light in said circuit or operating analogous signailing mechanism.

An object oi' another embodi nent or the invention is the provision of a thermo-responsive electrical switch assembly which completes an electrical circuit when said switch is brought to a predetermined temperature, thereby lighting up a signal light or activating equivalent mechamsm.

A further object of the invention is to provide type described of maximum simplicity, economy, ease of use, safety, and reliability.

Numerous other objects and advantages of the invention will be apparent as it is better understood from the following description, which, when considered in connection with the accompanying drawing, illustrates a preferred embodiment thereof.

In the drawing,

Figure l is a front elevational View of a thermo-responsive electrical switch assembly embodying the present invention;

Figure 2 is a view in central, Vertical, longitudinal section of the switch housing and associated parts, including a thermo-sensitive element for normal operation in closed circuit;

Figure 3 is a side elevational View of the switch assembly shown in Figure 2, taken at right angles thereto;

Figure 4 is a transverse vertical cross sectional view taken on line 4 4 of Figure 2;

Figure 5 is a front elevational view of a cartridge subassembly containing a thermo-sensitive element; for normal operation in closed circuit; and

Figure 6 is a front elevational view of a cartridge subassembly containing a thermo-sensitive element for normal operation in open circuit.

Like reference characters are used to designate similar parts in the drawing and in the description of the invention which follows.

Referring now more particularly to the drawing, the protective sheath l is made of a good heat conductor, such as metal, and is provided with external threads 2 for screwing the same into a railway car journal box or other place, the temperature of which is under surveillance. The hexagonal nut portion 3 on said external sheath provides means :for screwing the same tightly into the journal box. The sheath l is provided with a suitable cover 5, advantageously a knurled screw cap.

Within the sheath i is the housing 5, and electrically connected with said housing is the electric current supplying cable l. Said cable l may be provided with a plug S for connecting the switch assembly shown in Figure 1 into the rest of the electrical circuit, which includes a power source (not shown), and electrically actuated signalling or operating means (not shown), such as one or more electric lights, signal bells, electronic relays, etc.

Fig. 2 discloses the switch housing with a normally closed circuit type of thermo-responsive element therein. Said closed circuit construction is the preferred. form of the present invention. The housing is preferably made of shock absorbing or shock resistant material, such as tough plastic, and may have portions cut away to facilitatc visual inspection of the thermo-sensitive element and unrestricted heat transfer to thermosensitive element 9 housed therein.

As is more particularly apparent in Fig. 5, said thermo-sensitive element d for normal closed circuit operation may be sealed into a cartridge subassembly, comprising an insulating tube Il (advantageously made of glass to permit visual inspection of the element 9), a pair of perforated Stoppers l2 lmade of insulating material and pierced by said element 9, which they serve to position axially in said tube l l, and a pair of nuts ifi, i3. The ends of said element Si may be threaded, and said nuts i3, it may be screwed thereupon or otherwise suitably aiiixed to effect a tight seal between the Stoppers l2, l2 and the insulating tube il.

./is is especially apparent in Fig. 2, the housing 5 is provided with a hollow cap lll, secured to said housing 6 by the screw l5. Inside said hollow cap lll. the current supplying wires Hi and l'l are connected to electrical contacts i8 and l@ respectively. Contact i8 is electrically connected with the helical compression spring 2i. The other contact la is connected by means of the wire 22 with the threaded metallic bearing 23. Said bearing is on the end of said housing 6 distal from the hollow cap M.

The cartridge subassembly shown in Fig. 5 is dropped through the bearing 23, and the screw cap 2li is screwed into bearing 23. This thrusts the cartridge subassernbly against the spring 2l, whereby electrical contact is established from spring 2! through one nut I3 to one end of the thermo-sensitive element 9. The other end of said element completes the electrical circuit through the other nut i3, screw cap metallic bearing 23, wire 22, Contact l, and wire Il.

'Ehe switch and housing assembly shown in Fig. 2 is itted into the sheath .shown in Fig. l, and the screw cap 5 for said sheath is screwed thereover to complete the device as illustrated in Fig. l.

Our invention provides means for changing the character of the circuit when the switch reaches the critical temperature. By circuit changing we mean opening a previously closed circuit, or closing a previously open circuit, as the case may he. The subassembly of Fig. 5, when actuated, opens a normally closed circuit; the subassembly of Fig. 6, conversely, is actuated by the critical temperature to close a circuit which was previously open.

The subassembly of Fig. 6 comprises an insulating tube li with a pair of fusible electrodes 5, 2t inserted in opposite ends thereof. Each of said fusible electrodes comprises a head portion 23 adapted to lseal the end of the tube li;

d thereof. The assembly shown in Fig. l is placed in the space which is to be policed with respect to the occurrence of the overheating which it is desired to detect, and the plug 8 is connected into the signalling or controlling circuit. When the cartridge subassembly of Fig. 5 is used in the switch (as shown in Fig. 2), current will flow through the switch under normal operating conditions. When the switch is heated to the melting point of the thermo-sensitive element Si, said element melts, thereby opening the circuit and causing the signal light to go out, or otherwise indicating that the critical condition has occurred. Each signal light of course is appropriately marked to show the location of the switch connected therewith. After the overheating has been detected and corrected, the switch housing is opened by removing the screw cap 2li, and the burnt out cartridge subassembly is replaced by a new unit, thereby restoring the switch to operative condition. The burnt out cartridge subassernbly may be repaired simply by removing the melted thermonsensitive element 9 and replacing it with a new element.

a core portion 2l of relatively infusible electrically conducting material; and an annular ring 2S fusible at the actuating temperature of the switch. The two fusible electrodes 25, 25 are of such Vlength as to leave an air gap therebetween when they are assembled in the tube il. The switch for normally open circuit operation is completed by substituting the cartridge subassembly of Fig. 6 for the cartridge subassernbly of Fig. 5, in the switch illustrated in Figs. l, 2, and 3, the two cartridge subassemblies (those of Figs. 5 and 6) being interchangeable.

The operation of our improved thermally actuated switch is apparent from the construction When the embodiment utilizing the open circuit construction (see Fig. 6) is utilized, no current flows through the switch until the critical temperature is reached. At this temperature, the fusible annular ring 28 on each of the fusible electrodes 25, 25 melts, and the molten alloy or the like forms a pellet electrically connecting the core portions 2l, Zl of the two electrodes, thereby closing the circuit and causing an electric light to be illuminated7 a bell to be rung, an electronic relay to be actuated, etc.

in the embodiment of our invention utilizing a normally open circuit, the switch also may be reconstructed ysimply by replacing the fused cartridge subassembly with a new one; and the subassembly itself may be renovated by removing the fused electrodes and replacing them by a pair of new electrodes Z5.

An important advantage of our invention is that the switch may be converted from the normally closed circuit type to the normally open circuit type in a moment, simply by substituting the cartridge subassembly of Fig. 6 for that of Fig. 5, or vice versa.

A further advantage of our invention is that the same switch assembly may be set at will to actuate the signal mechanism at any arbitrarily preselected temperature. simply by providing the same with a thermo-sensitive element which .elts at the desired temperature. A large nurnber of alloys melting at a wide variety of sharply defined temperatures is known to the art, so that our improved switch be made to operate at almost any desired temperature.

In using our switch to police the journal boxes of railway cars, we advantageously select 220 as an appropriate signal temperature, since a heated journal at this temperature may be continued in service for some miles without injury to the journal or bearing, while said temperature of 226o F. in a journal box clearly indicates that something is wrong. We therefore find it advantageous to form the thermo-sensitive element or the fusible electrodes 25, foi-.this purpose of an alcy. which melts at 2202 F. In a iilie manner, if the preselected indicating ternperatruev is changed, the fusible alloy composition is adjusted accordingly.

lt is thought that the invention and many of its attendant advantages will be understood from the foregoing description, and it Iwill be apparent that various changes may be made in the form, construction and arrangement of the parts without departing from the spirit and the scope of the invention or sacrificing all of its material advantages, the form hereinbefore described being merely a preferred embodiment thereof.

We claim:

.1. A thermo-responsive electrical switch assembly for detecting eXcessive temperature in railway journal boxes, consisting of a metallic well, external threads thereon for screwing the same into a journal box, a housing of plastic material fitting thereinto, a glass tube in said housing, a rod of thermo-sensitive alloy in said glass tube and traversing the same, two plastic stoppers surrounding said rod and sealing the ends of said glass tube, a helical shock-absorbing compression spring in said housing thrusting endwise upon said glass tube and electrically two electrical conductors, one connected to each of said contacts; spring means to maintain electrical connection between said conductors and said contacts; and a heat conducting well encasing the entire switch assembly.

3. An electrical circuit breaker actuated by a predetermined temperature condition, comprising a nonconducting sealed envelop-e, a rod of fusible metallic alloy traversinCT said envelope and piercing opposite ends thereof, a housing for said envelope, an electrically conducting cap at one end of said housing, 'spring means in said housing electrically contacting one end of said alloy rod and thrusting the other end thereof against said electrically c'onducting cap, and two electrical supply wires, one connected to said spring means the other connected to said electrically conducting cap.

CHARLES M. ANGE JOSEPH B. BLACKBURN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 893,918 Gossick et al July 21, 1908 1,935,258 Ireland Nov. 14, 1933 1,734,071 Blalack Nov, 5, 1929 1,979,098 Clark Oct. 30, 1934 

